Method and apparatus for an improved sample capture device

ABSTRACT

A body fluid sampling device is provided. A mesh may be used to guide blood or fluid to travel directly from the wound to an analyte detecting port on the cartridge. Thus the volume of blood or body fluid produced at the wound site irregardless of its droplet geometry can be reliable and substantially completely transported to the analyte detecting member for measurement.

BACKGROUND OF THE INVENTION

Lancing devices are known in the medical health-care products industryfor piercing the skin to produce blood for analysis. Typically, a dropof blood for this type of analysis is obtained by making a smallincision in the fingertip, creating a small wound, which generates asmall blood droplet on the surface of the skin.

Early methods of lancing included piercing or slicing the skin with aneedle or razor. Current methods utilize lancing devices that contain amultitude of spring, cam and mass actuators to drive the lancet. Theseinclude cantilever springs, diaphragms, coil springs, as well as gravityplumbs used to drive the lancet. The device may be held against the skinand mechanically triggered to ballistically launch the lancet.Unfortunately, the pain associated with each lancing event using knowntechnology discourages patients from testing. In addition to vibratorystimulation of the skin as the driver impacts the end of a launcherstop, known spring based devices have the possibility of firing lancetsthat harmonically oscillate against the patient tissue, causing multiplestrikes due to recoil. This recoil and multiple strikes of the lancet isone major impediment to patient compliance with a structured glucosemonitoring regime.

When using existing methods, blood often flows from the cut bloodvessels but is then trapped below the surface of the skin, forming ahematoma. In other instances, a wound is created, but no blood flowsfrom the wound. In either case, the lancing process cannot be combinedwith the sample acquisition and testing step. Spontaneous blood dropletgeneration with current mechanical launching system varies betweenlauncher types but on average it is about 50% of lancet strikes, whichwould be spontaneous. Otherwise milking is required to yield blood.Mechanical launchers are unlikely to provide the means for integratedsample acquisition and testing if one out of every two strikes does notyield a spontaneous blood sample. It would be desirable to find improvedmethods to actuate the lancet.

As lancing devices have become more advanced, so have the sensors usedto measure the glucose levels in the blood samples. These analytesensors now operate using increasing lower volumes of blood sample. Someof these analyte sensors are designed for use with lancing devices thatcreate smaller wounds, which is beneficial in that there is less painand tissue damage, but also provide less blood to work with. As therequired amount of blood decreases, it becomes increasing important toguide the ever shrinking volumes of blood towards the sensor in anefficient manner that does not waste the small volumes of blood. At lowvolumes, it is desirable to regulate fluid flow so that the smallamounts of fluid are not wasted on surfaces that do not provide ananalyte measurement.

A still further problem concerns the possible inability to guaranteeblood flow from the finger lancet wound to the sensor port located onthe disposable cartridge. The problem might be the invariability of theblood volume from the lancet wound, otherwise known as the shape andsize of the droplet. There have been stated solutions such as thedelivery of the lancet to the finger with a deeper penetration depth ora programmed controlled “lancet-in-the-finger” dwell time to sustain thesize of the wound, which allows more blood to be produced from thewound. However, each might possibly result in a compromise on the degreeof pain or sensation felt by the patient.

In some embodiments, a capillary may be co-located with the lancet. Inorder to get the blood into the capillary, several variables (lateralmovement or other variation) come into play. Unless the blood droplet isdirectly centered on the capillary, there may be difficulty transportingenough blood to the analyte detecting member. For example, if there isany type of lateral movement or if the blood does not fall into thecapillary tube, it can smear on the side wall. With an integratedsampling configuration where it may be difficult to visualize where theblood or body fluid is going, there may be no way for the subject torectify the situation by milking the finger to get a larger droplet andincrease the potential of getting the blood in.

The design of these improved medical devices has also challengedengineers to come up with more efficient methods of design. Withmacroscopic devices, such as conventional blood chemistry analyzers orflow cytometers, it is usually possible during the development phase tomount flow sensors, temperature probes, and optical detectors at variouspositions along the instrument pathway to experimentally determine theoptimum operational parameters for the device. However, this approachoften fails for microdevices because standard sensors and probes aretypically of the same scale as the microdevice and interfere so muchwith device behavior that the measured data do not represent actualdevice performance. Thus it would be desirable to come up with designmodels where the most useful experimental data tend to be externalmeasurements from which the internal physics of the microdevice shouldbe deduced.

SUMMARY OF THE INVENTION

The present invention provides solutions for at least some of thedrawbacks discussed above. The technical field relates to guiding afluid sample obtained from the body for analysis. Because of the lowfluid volumes envisioned for improved sensing devices, the ability toefficiently guide the small sample volumes to a targeted area is ofinterest. Specifically, some embodiments of the present inventionprovide a body fluid sampling device with improved fluid control.Preferably, the improved fluid control is easy to use. At least some ofthese and other objectives described herein will be met by embodimentsof the present invention.

In one aspect, the present invention provides surface texturing thatcorrals or guides fluid in areas that desire to receive the fluidsample. The texturing may also be used in combination with other surfacetreatments such as coatings. Texturing, however, it a more permanentsolution.

In one embodiment, a radial cartridge is provided that has a pluralityof penetrating members and a plurality of analyte detecting memberswhere texturing near the detecting members guides the fluid to themembers. The texturing may be formed by a variety of techniques as knownin the art and can be formed in various geometries. The presentinvention allows very small volumes of fluid to be guided by restrictingits flow due to surface texturing.

In another aspect of the present invention, the invention relates tousing an electronic tissue penetration device to drive a penetratingmember into tissue, sample the body fluid, and measure analyte levels inthe body fluid using a sensor cartridge. The invention uses varioustechniques to draw body fluid towards an analyte detecting device on thecartridge.

Embodiments of the present invention provide solutions to a problem,which concerns the possible inability to guaranteed a stable bloodvolume from a finger lancet wound to a sensor port located on adisposable cartridge. The problem might be due to shallowness of thelancet penetration depth, skin surface tension issues, or the patient'svascular conditions resulting in the invariability in achieving anadequate blood droplet shape and size. There have been other statedsolutions such as the delivery of the lancet to the finger with a deeperpenetration depth or a control method to increase the amount of blood tobe produced from the wound.

In one embodiment, this invention produces a concept of a capillary needfor the blood to travel directly from the wound to the sensor port onthe cartridge. Thus the volume of blood produced at the wound siteirregardless of its droplet geometry can be completely transported tothe analyte detecting member.

In a still further aspect, the present invention provides solutions forat least some of the drawbacks discussed above. Specifically, someembodiments of the present invention provide an improved, integratedfluid sampling device. To improve device integration, devices andmethods for connecting sensor regions to contact pad regions may beprovided. One of the problems involves getting electrical contact withthe leads connected to electrodes coupled to the sensor regions. Atleast some of these and other objectives described herein will be met byembodiments of the present invention.

In yet another aspect, the technical field of the invention relates tothick film conductor depositions for the purpose of providing sensorydevice placement, signal conduction, and isolation from environmentsdetrimental to the sensory device storage and integrity prior toutilization.

In one embodiment, the present invention provides solutions for at leastsome of the drawbacks discussed above. The invention relates to theelectronically controlled actuation of a lancet to create a wound forthe collection of a blood sample for analysis. Specifically, someembodiments of the present invention provide an improved fluid samplingdevice. Because of the obtain spontaneous blood generation in arelatively painless manner, the ability to move the penetrating memberat a high, yet controllable velocity is of interest. At least some ofthese and other objectives described herein will be met by embodimentsof the present invention.

In another aspect of the present invention, the invention relates tousing the electronic tissue penetration device to drive a penetratingmember into tissue, wherein a elastomeric portion actuated by theelectronic device to drive the penetrating member. More specifically,the invention relates to the electronic actuation of a lancet throughthe use of an elastomeric capacitor that can be made to change lengthwith the application of voltage across the capacitor plates.

In one embodiment, a method of body fluid sampling is provided. Themethod comprises moving a penetrating member at conforming to aselectable velocity profile or motion waveform by using electricity toactuate and elastomeric device and measuring the position of thepenetrating member. In some embodiments, the device will use theposition data to create a feedback loop wherein the actuator will movethe penetrating member at velocities that follow a desired trajectory.

Still further, the present invention provides solutions for at leastsome of the drawbacks in designing medical devices. The technical fieldrelates to methods for designing microscale devices. Because thedifficulty of building such sensors for testing, the ability of thepresent invention to accurately model the microscale device is ofinterest. Specifically, some embodiments of the present inventionprovide an improved method and model for developing such microscaledevices. At least some of these and other objectives described hereinwill be met by embodiments of the present invention.

Embodiments of the present invention disclosed herein comprise the useof a mathematical modeling algorithm to develop a list of design rulesfor dispersed-phase-based biosensors. Furthermore, various pieces ofhardware as well as embodiments of a glucose detecting member aredisclosed.

The system may further comprise means for coupling the force generatorwith one of the penetrating members.

The system may further comprise a penetrating member sensor positionedto monitor a penetrating member coupled to the force generator, thepenetrating member sensor configured to provide information relative toa depth of penetration of a penetrating member through a skin surface.

The depth of penetration may be about 100 to 2500 microns.

The depth of penetration may be about 500 to 750 microns.

The depth of penetration may be, in this nonlimiting example, no morethan about 1000 microns beyond a stratum corneum thickness of a skinsurface.

The depth of penetration may be no more than about 500 microns beyond astratum corneum thickness of a skin surface.

The depth of penetration may be no more than about 300 microns beyond astratum corneum thickness of a skin surface.

The depth of penetration may be less than a sum of a stratum corneumthickness of a skin surface and 400 microns.

The penetrating member sensor may be further configured to controlvelocity of a penetrating member.

The active penetrating member may move along a substantially linear pathinto the tissue.

The active penetrating member may move along an at least partiallycurved path into the tissue.

The driver may be a voice coil drive force generator.

The driver may be a rotary voice coil drive force generator.

The penetrating member sensor may be coupled to a processor with controlinstructions for the penetrating member driver.

The processor may include a memory for storage and retrieval of a set ofpenetrating member profiles utilized with the penetrating member driver.

The processor may be utilized to monitor position and speed of apenetrating member as the penetrating member moves in a first direction.

The processor may be utilized to adjust an application of force to apenetrating member to achieve a desired speed of the penetrating member.

The processor may be utilized to adjust an application of force to apenetrating member when the penetrating member contacts a target tissueso that the penetrating member penetrates the target tissue within adesired range of speed.

The processor may be utilized to monitor position and speed of apenetrating member as the penetrating member moves in the firstdirection toward a target tissue, wherein the application of a launchingforce to the penetrating member is controlled based on position andspeed of the penetrating member.

The processor may be utilized to control a withdraw force to thepenetrating member so that the penetrating member moves in a seconddirection away from the target tissue.

In the first direction, the penetrating member may move toward thetarget tissue at a speed that is different than a speed at which thepenetrating member moves away from the target tissue.

In the first direction the penetrating member may move toward the targettissue at a speed that is greater than a speed at which the penetratingmember moves away from the target tissue.

The speed of a penetrating member in the first direction may be therange of about 2.0 to 10.0 m/sec.

The average velocity of the penetrating member during a tissuepenetration stroke in the first direction may be about 100 to about 1000times greater than the average velocity of the penetrating member duringa withdrawal stroke in a second direction.

A further understanding of the nature and advantages of the inventionwill become apparent by reference to the remaining portions of thespecification and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded view of one embodiment of a cartridge with sealinglayer and analyte detecting layer according to the present invention.

FIG. 2 shows a close-up view of one portion of the cartridge of FIG. 1.

FIGS. 3A-3H show examples of geometries for texturing formations.

FIG. 4 shows a perspective view of a ring of analyte detecting membersthat may have texturing.

FIG. 5 shows another embodiment of the present invention with texturing.

FIG. 6 shows a cross-section view of yet another embodiment of thepresent invention with texturing.

FIG. 7 shows one embodiment of a mesh for use with the presentinvention.

FIG. 8 shows perspective views of a fluid sampling device and acartridge for use with such a device.

FIG. 9 shows a close-up view of one embodiment of a cartridge usingmesh.

FIGS. 10-14 show other views of embodiments of mesh for use with thepresent invention.

FIG. 15 shows one embodiment of electrical contacts and leads for usewith the present invention.

FIG. 16 shows one embodiment of the present invention with contact padsfor use with commutators.

FIG. 17 shows an exploded view of a cartridge with an analyte detectingmember layer.

FIG. 18 shows a perspective view of one embodiment of the presentinvention for use with commutators on the inner diameter of thecartridge.

FIG. 19 shows a cross-sectional view of one embodiment of the presentinvention.

FIG. 20 shows yet another embodiment of the present invention.

FIGS. 21-22 show side views of actuators according to the presentinvention.

FIGS. 23A-23B show two different embodiments of actuators according tothe present invention.

FIG. 24 is a schematic for determining position for an actuatoraccording to the present invention.

FIGS. 25A-25D show penetrating member velocity profiles.

FIG. 26 is a schematic showing one embodiment of feedback control for apenetrating member.

FIGS. 27A and 27B are perspective views of a fluid sampling device and acartridge for use with such a device.

FIG. 28 is a diagram showing the analyte detecting member as modeledafter initial contact of the member and the fluid sample.

FIGS. 29 a and 29 b are charts showing reaction rates of enzymereactions on the sample-sensor interface.

FIGS. 30 a and 30 b are charts showing concentrations profile of enzymesalong the sample-sensor interface.

FIG. 31 a through 31 c are charts showing concentrations of reactantsalong the sample-sensor interface.

FIG. 32 is chart showing change in fluorescence lifetime as a functionof analyte detecting member response to glucose.

FIGS. 33 a and 33 b are charts showing simulated dynamic calibration (33a) and response (33 b) graphs of modeled glucose analyte detectingmember.

FIG. 34 shows experimentally obtained response curve of an analytedetecting member designed according to the model predictions accordingto the present invention.

DESCRIPTION OF THE SPECIFIC EMBODIMENTS

The present invention provides a multiple analyte detecting membersolution for body fluid sampling. Specifically, some embodiments of thepresent invention provides a multiple analyte detecting member andmultiple penetrating member solution to measuring analyte levels in thebody. The invention may use a high density design. It may usepenetrating members of smaller size, such as but not limited to diameteror length, than known lancets. The device may be used for multiplelancing events without having to remove a disposable from the device.The invention may provide improved sensing capabilities. At least someof these and other objectives described herein will be met byembodiments of the present invention.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the invention, as claimed. It must be notedthat, as used in the specification and the appended claims, the singularforms “a”, “an” and “the” include plural referents unless the contextclearly dictates otherwise. Thus, for example, reference to “a material”may include mixtures of materials, reference to “a chamber” may includemultiple chambers, and the like. References cited herein are herebyincorporated by reference in their entirety, except to the extent thatthey conflict with teachings explicitly set forth in this specification.

In this specification and in the claims which follow, reference will bemade to a number of terms which shall be defined to have the followingmeanings:

“Optional” or “optionally” means that the subsequently describedcircumstance may or may not occur, so that the description includesinstances where the circumstance occurs and instances where it does not.For example, if a device optionally contains a feature for analyzing ablood sample, this means that the analysis feature may or may not bepresent, and, thus, the description includes structures wherein a devicepossesses the analysis feature and structures wherein the analysisfeature is not present.

FIG. 1 shows one embodiment of a radial cartridge 20. The cartridge 20may include a sterility barrier 22 and a substrate 24 having a pluralityof analyte detecting members 26. In this embodiment, the cartridge 20 isdesigned so that blood will enter the fluid chamber 30 and be held therefor analysis.

Referring now to FIG. 2, a close up view of one embodiment of the samplechamber 30 is shown. As discussed, it is often desirable to have ahydrophilic surface in certain areas when trying to create fluid flow.However, as seen in FIG. 2, having a flat surface that is hydrophilicmay cause the fluid sample 32 to spread all over the sample chamber 30.

In one embodiment of the present invention, surface texturing may beused to address the issue. Although not limited to the following,texturing may also be combined with chemical surface treatments or othersurface treatments. To design the texture, one may need to account forthe surface tension (contact angle), the bulk properties (density, etc.)and surface flow. Since the volumes that the present invention dealswith may be, as a nonlimiting example, in the area of about 250-500 nl,just having blood flow around, is something that the device cannotafford. It is desired that the fluid flow be a shaped flow, because atlow volumes, the fluid cannot be wasted on errant flows.

At low volumes, there is no conservation, and the blood goes everywhere.For one nonlimiting example where it is desired that the blood or fluidgoes into a tube. However, the preferential path is the surface anduntil the tube fills completely and creates a pressure differential, theblood is not all going in there. The blood could try to pull but thefluid could “break” and then not all of the blood is pulled into thetube and into the device for measurement.

In one embodiment, the present invention essentially involves texturingto direct the flow. For example and not limitation, the texturing may beon the cartridge 20 or it may be along fluid paths formed by thecartridge 20. This is one solution for tubular designs (i.e. capillarytube). Playing with the flow equation allows for designing of thetexturing, but meshes are different animals since they create increasedsurface area. The tubular problem, such as guiding fluid into a sensorarea or a capillary tube involves positioning the fluid to engage thecapillary. In one embodiment, a single material is used. The materialmay be an ideal flow material for use with a single molding. Multiplemoldings/laminated moldings may be used. As a nonlimiting example,materials may have a contact angle in the area of about 20 to 5 degrees.

FIGS. 3A-3H show examples of geometries that may be used with thepresent invention. These are purely exemplary and are nonlimiting.Additionally, roughing or texturing the surface may improve userfeedback, letting them know whether they are on target. It might helpwith the sensation of contact. The texturing may be dimples, raisedportions, detents, depressions, cross-hatch, scoring, criss-cross,triangles, any of a variety of other surface geometries, and/or anysingle or multiple combinations of the above.

FIG. 3A shows an embodiment where the texturing 40 is in a circularstructure shape around an opening 42 for receiving body fluid. In thisembodiment, the texturing 40 is designed to “corral” fluid towards theopening 42. FIG. 3B show texturing 44 in a parabolic shape. As seen inFIG. 3B, the texturing does not necessarily fully surround the opening42. FIG. 3C shows texturing 46 in an elliptical configuration. FIG. 3Dshows texturing 48 in a horseshoe configuration. FIG. 3E shows texturing50 in a box configuration. FIG. 3F shows texturing 52 in a rectangularconfiguration. FIG. 3G shows texturing 54 in a curved-linearconfiguration. FIG. 3H shows texturing 56 in a teardrop-heart shape. Itshould be understood that polygonal, hexagonal, triangular, or othershapes may also be used. The texturing can be placed on any surface andis not limited to being placed on the surface shapes shown. Someembodiments may have single or multiple combinations of the aboveshapes.

For changing surface property of Teflon and other materials, you canchemically attack it. As an example, the chemical attack may result inabout 30 angstroms of surface change. By texturing, it forms and staysin that ring. But in the middle it starts to move into the sensor area(since the other areas are corralled). In some embodiments, a funnelarea may be located at center of the “corral”. We are affecting thesurface properties by texturing.

As a nonlimiting example, the texturing may be used with a typical 300micron diameter lancet. The blood droplet could form anywhere on thelancet. It's also a C-shaped wound created on the patient. The cuttingedge creates that shape. Anywhere around this, droplet can go in thecenter, or anywhere around the C. That why the texturing is used tocorral fluid that may hit the surface and need to be guided. In someembodiments, there could be gaps in the texturing so that fluid anddirected in certain directions.

Types of texturing includes but is not limited to lumpy, bumpy (justtexturing) round dots, square dots, etc. . . . . Texturing may be formedby any variety of techniques including but not limited to aiming aplasma beam to create the texturing; sacrificial foam/hot pressembossing; chemical texturing, combinations of the above, and othertechniques as known in the art.

Referring now to FIG. 4, one embodiment of a ring 60 for use with acartridge such as that shown in FIG. 1, will now be described. Thisembodiment of a ring 60 having a plurality of analyte detecting members62 is shown. For example and not limitation, the ring 60 may be formed alinear tape of analyte detecting member 62 formed into a circularconfiguration. The analyte detecting member 62 may include an aperture64 to allow for a penetrating member (not shown) to pass through topenetrate tissue. In the present embodiment, the analyte detectingmember 62 may have three electrodes 68, 70, and 72. The electrodes arecoupled to the appropriate electrical contacts 74. The present inventionmay also include texturing 40 on the analyte detecting member 62.

It should be understood that in some embodiments, the linear tape ofanalyte detecting members 62 may be “folded” in a reverse manner so thatthe outer surface 80 of the ring 62 will now be the inner surface (orinner diameter) of the ring 62. Thus the leads 74 will be on the innersurface and the plain backing 82 will now face outward. In such aconfiguration, the backing 82 would now have the texturing as shown inFIGS. 3A-3H. Having this reverse configuration allows the electrodes tobe on the side of the analyte detecting member that first receives bodyfluid as indicated by arrow 1234. The embodiment of FIG. 4 may also beformed or attached to the outer circumferential surface of thecartridge.

Referring to FIG. 4, the orientation of the analyte detecting members 62is orthogonal to the orientation of the penetrating member. Thepenetrating member moves through the aperture 64, through a samplecapture port (not shown) to pierce into the skin or tissue and retract.In one embodiment, the blood sample may move by capillary or wickingaction across the electrodes 68, 70, and/or 72. There may be wickingmaterial used on all or part of the sample capture or transport area.The sample volume for this configuration is relatively small, less than300 nl. In some embodiments, the amount in the analyte detecting memberis about 60 to 70 nl. The required space for the capillary andelectrodes is relatively small, less than 20 mm². In one embodiment, therange of the aperture 64 is about 0.5-1.0 mm.

FIG. 5 shows yet another embodiment of the present invention which mayuse texturing 40. This embodiment may use individual analyte detectingmembers 90 and mated with a cage 92 to hold them in position for usewith a disc or cartridge containing a plurality of penetrating members.The cage 92 may be integrally formed with the cartridge 20 holding theplurality of penetrating members or it may be formed separately and thencoupled to the cartridge. As seen in FIG. 5, some embodiments of thedevice may have fewer than 50 penetrating members, such as but notlimited to 17, 20, 25, 30, or 40 penetrating members.

Referring now to FIG. 6, a cross-section of yet another embodiment ofthe present invention will now be described. This cross-section shows acartridge 100 holding a penetrating member 102 in a cavity 104. From awound created in target tissue by the penetrating member 102, body fluidwill contact electrodes 108 positioned around the exit port 110 of thepenetrating member 102. It should be understood that the electrodes 108may be arranged in a variety of configurations about the exit port 110.Some embodiments may have all the electrodes 108 below the port 110.Some embodiments may have all of the electrodes 108 above the port 110.Some may have the members 108 distributed about the opening. Someembodiments may have a mesh that covers the members 108 or comes next tothe members and brings body fluid to the members 108. In still otherembodiments an outer ring portion 114 maybe formed separate from portion116 and then the two portions are integrally joined to form a singleintegral unit. The joining may occur by adhesives, bonding, heatbonding, interlocking coupling, or other methods. This may facilitatemanufacture of parts that may use different sterilization methods. Asterility seal (not shown) such as but not limited to a foil may beplaced over the outer circumference of the ring and may be peeled backto open each individual port 110. In other embodiments, the sterilityseal may be punched open by a device such as but not limited to aseparate punch device, the penetrating member, or a combination of thetwo. By example and not limitation, the device may include texturing 48around the electrodes 108 or a larger area of texturing 40 thatsurrounds all the electrodes at once (not shown).

Referring now to FIG. 7, one embodiment of the present invention willnow be described. Rather than let a droplet of body fluid build on thesurface, one concept is to pull the droplet from the surface with, as anonlimiting example, a fine mesh 120 that is located between thepenetrating member and the finger. FIG. 7 shows a top down view of aradial cartridge 121 having the fine mesh 120. At the start position,the lancet mesh 120 may be located between the lancet tip and the foil.When cutting the foil, prior to the lancing event, the cuttinginstrument will spare the fragile mesh. In this embodiment, the amountof foil can be relatively limited because the mesh will be able to wickthe blood down to the analyte detecting member. With the lancet tipbeing very sharp, the mesh 120 would be pushed to the side rather thancut. The resulting ring of capillary fibers around the wound channelwould be available after the lancet was retracted to wick the bloodsample into the sample channel.

FIG. 8 shows the radial cartridge 121 for use with a lancing device 130.The radial cartridge 121 may be sealed with a sterility barrier 132 andbe coupled to analyte detecting members mounted on a substrate 34. Asuitable device is described in commonly assigned, copending U.S. patentapplication Ser. No. 10/429,196 fully incorporated herein by referencefor all purposes.

Referring now to FIG. 9, as described above, when a penetrating member40 is actuated and extends outward from the cartridge 121, the mesh 120is pushed aside or pierced by the exiting member 140. The resulting ringof capillary fibers 142 around the wound channel would be availableafter the lancet was retracted to wick the blood sample into the samplechannel.

The physical characteristics of the mesh 120 is one aspect forsuccessfully transport of blood to the analyte detecting member 150. Inone embodiment, the mesh 120 could be pliable enough the allowrelaxation, but maintain contact or near-contact with the skin surface.An active region could be striped on the mesh to allow the blood to onlytravel in the direction towards the analyte detecting member. Adifferent gauge capillary fiber may be used on the mains versus thecross. In another embodiment, the mains may have a smaller gage andhigher pitch to promote vertical movement. As an additional benefit, ifthe mesh assisted in distributing the force of lancet impact with theskin, the cutting efficiency of the lancet could be increased.

In another embodiment, the mesh 120 would reduce the amount ofmicropositioning used to assure that the droplet of body fluid gets tothe analyte detecting member. The potential volume required by theanalyte detecting member could be reduced by reducing the amount ofblood or body fluid that spontaneously rises to the surface of the skinthat is either not removed from the skin once the surface tension isreleased in a traditional, microfluidics methods. Traditionalmicrofluidics could also have a higher volume required to get the bloodto the sample chamber.

Referring now to FIG. 10, it should be understood that the mesh may beconfigured to a variety of geometries. The mesh 120 could be fabricatedas a ring as sees in FIG. 7 and then heat sealed into the analytedetecting member. The heat sealing should not effect the integrity ofanalyte detecting member. By example and limitation, the mesh 120 mayalso be used to cover at least one or more electrodes 68, 70, and 72used in the device of FIG. 4. In some embodiments, the mesh 120 may alsobe used to cover the aperture 64.

As seen in FIG. 11, the mesh 120 may be configured so that a blooddroplet 160 that hits the mesh 120 will be drawn toward the analytedetecting member 150 as indicated by arrow 162, due to the length of themesh 120 which is extended down to the member 150. As seen in FIG. 10,which is a top down view, the mesh 120 has portions 164 which may beextended down towards the member 150.

In one embodiment, a capillary mesh may be used that basically allowsthe lancet to fire through or the lancet can come around or through alancet aperture in the mesh. The mesh in one embodiment may be ahydrophilic mesh that would then allow the blood to be absorbed, in thisembodiment, once the droplet is built up on skin. With mesh, it does notmatter where the droplet hits it. With a certain volume, there is enoughblood to coat the mesh and coat the analyte detecting member, thuscreating a better solution for integrated analyte detecting member.

FIG. 12 shows one embodiment where the force of the penetrating member140 impacting the mesh 120 flattens it out and pushes it against theskin. In this particular embodiment of mesh 120, the mesh 120 is pliableenough to allow relaxation.

One issue associated with the present invention may be getting theanalyte detecting member close enough to the lancet. In manyembodiments, the radial axis of the lancet is going to be where thedroplet of body fluid is going to form. The pickup or transport is goingto have to come to the droplet to acquire it.

In one embodiment, a layer of body fluid at least 50-100 microns thickis desired, and this is the thickness that the electrode needs togenerate the glucose signal. So if the mesh is sandwiched on top of theelectrode or if fluid is wicked along the capillary mesh, it is possibleto repeatable transport blood to the analyte detecting member.Electrodes tend to be hydrophobic. But if there is a hydrophilic mesh,it will still travel to the mesh, even though the surface energy is low.

In another embodiment, a particularly high energy capillary mesh can beco-located at where the droplet is going to come which is at the axis ofthe lancet travel. The wicking member would be heat sealed to theelectrode. Most preferable is a design where the wick is at about 90degrees (i.e. vertical) as seen in FIG. 13.

Referring now to FIG. 14, it should be understood that the mesh may be agradient type of mesh. It may have high energy to pull one way asindicated by arrows 180. The crosses and the mains on the mesh may bedesigned and patterned to created a desired movement of fluid in contactwith the mesh. The resulting effect is a gradient. A thinner gauge maybe used in a higher energy area. With regard to the capillary size andthe gaps, they are relatively proportionate. Of course, when you getdown to a level below 100 microns, 70 microns for the pore size, themesh can get into blood filtration or clogging of the blood,particulates such as the big lucocytes tend to clog and make the meshunproductive/effective anyways. There is a limit to how much you canplay with sizing of the mesh strands.

It should be understood, of course, that the present invention mayoperate with alternative embodiments. With the mesh, you may be able touse a hydrophilic spray. Or to create a highly texturized surface orother surface treatment, the mesh may direct the flow of fluid. In somealternative embodiments, a ribbed plastic without pores may be used. Onelimitation of traditional capillary structure is that when it gets tooclose to the skin, it tends to blanche or inhibit the movement of bloodto the surface. So even if you have it perfectly located in a lateral,collateral direction. Such a capillary structure is vertically sensitiveand sometimes does not get the blood as a result.

If the mesh is very compliant, then the vertical sensitivityproblem/blanching is substantially resolved. The mesh could beco-located perfectly and touching the surface of the skin. And then youdo not have a vertical offset or a vertical insensitivity problem thattends to blanche. Then because there is not a bearing surface there andpressure is kept at a level below that which would cause blanching.

FIGS. 15 and 16 provide additional details of the line conductors,feed-throughs, and conductor pads. The embodiment shown in the FIGS. 15and 16 may be adapted for use with a radial cartridge such as that shownin commonly assigned, co-pending U.S. patent application Ser. No.10/429,196 filed May 1, 2003, fully incorporated herein by reference forall purposes. For example and not limitation, FIG. 15 shows a supportstructure 212 that is adapted for use with a radial cartridge 20. Thesupport 212 may include a plurality electrodes such as, but not limitedto, a working electrode 240, a counter electrode 242, and a referenceelectrode 244. A plurality of conduction lines 250 may be used as leadsto connect the electrodes having the sensory material 214 with thecontact pad 230 on the other side of the support 212 (see FIG. 16). Byexample and not limitation, the contact pad 230 may be substantiallylarger in width than the conduction lines 250. This facilitates thetolerance of the pad to slight misalignments of the pad with connectorsor contacts on a measurement device. The contact pads 230 are shown tobe square or rectangular in geometry. It should be understood, however,that the contact pads 230 may be circular, oval, polygonal, triangular,any single combination of the geometries above, or any combination ofany number of the geometries above. The via holes may also besufficiently spaced apart such that there is sufficient space on theunderside of the support structure to accommodate the larger contactpads 230.

In the present embodiment, the top side of the support 212 may include asealing region 260. This sealing region 260 may be used to keep thesensor material 214 in a sealed environment prior to use.

FIG. 17 shows how one embodiment of a radial cartridge 201 may becoupled to a sterility barrier 203 and a support 212 having the sensormaterial 214 and contact pads 230. Of course, the support 212 of FIG. 17may be configured to include configuration shown in FIGS. 15 and 16. Thesupport 212 would be sealed, in one embodiment, against the underside ofthe radial cartridge 201. This integrates the sensory material 214 withthe cartridge and also creates the sealed environment in which thematerial 214 may be stored until ready for use.

Embodiments of the present invention take the sensor electrode contactpad which for example and not limitation, may be located anywhere on thebottom on the package taking advantage of the disc shape. The electrodecontact pads may be placed anywhere along the disc (between ID and OD).A commutator pickup may be used to make electrical contact. In oneembodiment, a million insertion point probe may be used that isspring-loaded into the door or housing of the device. Other embodiments,by way of example and not limitation, may use gold plated sheet metalprobes that are bent up. As the disc-shaped cartridge rotates, the nextchamber rotates right in line with the contacts.

Referring now to FIG. 18, one embodiment of the present invention coulduse a commutator 200 to engage the electrode leads 202. The commutator200 may be spring loaded to better engage the leads. As the cartridgerotates as indicated by arrows 204, those lead from electrodes in theactive regions come in contact with the commutator 200. Referring backto FIG. 16, it can be sent that commutators 200 may be positioned toengage contact pads from the leads, where the pads 230 are notpositioned in the inner diameter of the cartridge. The pads 230 may beon the underside, side, or somewhere along the length of the cartridge.It should be understood that a variety of commutators 200 are shown inFIG. 18. The device may have one set of commutators or it may havemultiple sets. They may all have the same orientation or combinations oforientations. FIG. 18 shows side by side, vertical, and spring basedversions. These are purely exemplary and are nonlimiting.

Referring now to FIG. 19, other embodiments may have the commutators onthe outer diameter of the cartridge. FIG. 19 shows a cross-section ofyet another embodiment of the present invention will now be described.FIG. 19 shows a cartridge 20 with a penetrating member 102. In oneembodiment, a ring portion 270 is coupled to the cartridge 20. In someembodiments, the ring portion 270 may be integrally formed with thecartridge 20. In other embodiments, the two portions are integrallyjoined to form a single integral unit. The joining may occur byadhesives, bonding, heat bonding, interlocking coupling, or othermethods. This may facilitate manufacture of parts that may use differentsterilization methods. An opening 273 may be provided to allow anysterility seals on the cartridge 20 to be opened. A punch or othermechanism may extend down through the opening 273 to piece the seal andclear it from the path of the penetrating member 102.

As seen in FIG. 19, an analyte detecting member 275 may be housed in theportion 270. The analyte detecting member 275 may be similar toembodiments shown in FIGS. 110-112. A groove 1330 in the portion 270 maybe formed to hold the member 275. A plurality of analyte detectingmembers 275 may also be placed on a ribbon and then placed in a groove277 that runs around the circumference of the disc. Openings 279 allowfor the penetrating member to exit. By way of example and notlimitation, some embodiments may have texturing 40 around the openings279 to control any wayward fluid flow. The texturing 40 may also bepresent on the detecting member 275.

FIG. 19 also shows that commutators 200 may also be used with thepresent invention. In some embodiments the commutators 200 may be springloaded to press against contacts 281 to ensure a solid contact. By wayexample and not limitation, the contacts 281 and commutators may also beon the inner diameter of the analyte detecting member 275. Otherembodiments may have the contacts 281 on the bottom of the analytedetecting member 275. Some embodiments may have the members 275 extendbelow the bottom surface of the cartridge 20 to facilitate engagementwith the commutators 200. Other embodiments may have the bottom of thedetecting member 275 substantially flush with the bottom surface ofcartridge 20. The contact pad 281 may be on the bottom surface of thedetecting member 275. In some embodiment, there may be a groove 283(shown in phantom) that allows for commutators 200 to engage any contactpads on the inner diameter. In some embodiments, a similar groove may beon the outer diameter side to facilitate contact with contact pads onthat side.

Referring now to FIG. 20, a still further embodiment of the presentinvention will be described. In one embodiment of the lancing device,the cartridge goes in, foil-side up. If we print on sensors 218 in thechamber, you could have the probes 220 go through the printed material224, making contact with the sensors. In this embodiment, electrodes atall. In some alternatives, cam action may be used to move the probes outof the way. They go back in, making contact with the next chamber whenthe cartridge is rotated into place. Thus to get rid of the electrodes,we want to make contact with the printed sensor using a needle probewhich may be made by way of example and not limitation, laser etchedgold. Alternative embodiments may use laminates. They use variousthicknesses of materials. In some embodiments, the probes do notpenetrate the sensors in a manner that contacts blood.

Referring now to FIG. 21, an embodiment of the present invention usingan elastomeric actuator will now be described. The present inventionconsists of an electronic actuator 300 consisting of a soft elastomersheet 302 with electrodes 304 applied to the opposing large surfaces.The geometry created is that of a capacitor. When electrical potentialis applied to the electrodes, electrostatic forces attract theelectrodes toward each other. As seen in FIG. 22, the intervening softelastomer is displaced by the electrodes, lengthening the elastomer.This displaced material 310 acts to elongate the elastomer/electrodeassembly. Because the elastomer grows in length, it is desirable in oneembodiment to construct the electrodes from a compliant material, suchas carbon-loaded silicone (SRI patent), so they can conform to theelongated elastomer.

It has been observed that pre-stretching the elastomer (SRI) improvesresistance to dielectric breakdown, and an extension of the operatingvoltage range. The actuator embodiment shown in FIG. 23A consists of arigid frame 312 with a clamp 314 at one end to hold the elastomer. Atthe other end of the frame a guide bearing holds an actuator shaft thatis clamped to the other end of the elastomer 316. A pre-stretch spring318 tensions the elastomer. A controlled voltage source 319 appliesactuating voltage to the electrodes on the elastomer.

A second style of actuator shown in FIG. 23B consists of a pre-tensioneddiaphragm 330 stretched over a chamber. In this embodiment, an actuatorshaft 332 is attached to the center of the diaphragm 330, and may beguided by a bearing (not shown) if needed. Electrodes applied to thediaphragm 330 cause it to expand. To shape the diaphragm, and direct theresulting motion, a bias pressure from a source 334 is applied behindthe diaphragm. The same function can be achieved by adding a bias springto the actuation shaft.

Referring now to FIG. 24, one component of an actuator system isposition feedback. A position signal can be obtained from an elastomericactuator by measuring the capacitance of the actuator 330 (or 316). Thiscan be accomplished by imposing a sine wave, or pulse signal 320 ontothe DC drive voltage. The current resulting from this sensing signal isa measure of the capacitance of the actuator, and hence the deflectionof the electrode plates.

As seen in FIGS. 25 and 26, a variety of feedback systems and velocityprofiles may be used to control the motion provided by actuator 330 or316. As discussed above, tissue penetration devices which employ springor cam driving methods have a symmetrical or nearly symmetricalactuation displacement and velocity profiles on the advancement andretraction of the penetrating member as shown in FIGS. 25 and 26. Inmost of the available lancet devices, once the launch is initiated, thestored energy determines the velocity profile until the energy isdissipated. Controlling impact, retraction velocity, and dwell time ofthe penetrating member within the tissue can be useful in order toachieve a high success rate while accommodating variations in skinproperties and minimize pain. Advantages can be achieved by taking intoaccount of the fact that tissue dwell time is related to the amount ofskin deformation as the penetrating member tries to puncture the surfaceof the skin and variance in skin deformation from patient to patientbased on skin hydration.

In this embodiment, the ability to control velocity and depth ofpenetration may be achieved by use of a controllable force driver wherefeedback is an integral part of driver control. Such drivers can controleither metal or polymeric penetrating members or any other type oftissue penetration element. The dynamic control of such a driver isillustrated in FIG. 25C which illustrates an embodiment of a controlleddisplacement profile and FIG. 25D which illustrates an embodiment of athe controlled velocity profile. These are compared to FIGS. 25A and25B, which illustrate embodiments of displacement and velocity profiles,respectively, of a harmonic spring/mass powered driver. Reduced pain canbe achieved by using impact velocities of greater than about 2 m/s entryof a tissue penetrating element, such as a lancet, into tissue. Othersuitable embodiments of the penetrating member driver are described incommonly assigned, copending U.S. patent application Ser. No. 10/127,395filed Apr. 19, 2002 and previously incorporated herein.

FIG. 26 illustrates the operation of a feedback loop using a processor360. The processor 360 stores profiles 362 in non-volatile memory. Auser inputs information 364 about the desired circumstances orparameters for a lancing event. The processor 360 selects a driverprofile 362 from a set of alternative driver profiles that have beenpreprogrammed in the processor 360 based on typical or desired tissuepenetration device performance determined through testing at the factoryor as programmed in by the operator. The processor 360 may customize byeither scaling or modifying the profile based on additional user inputinformation 364. Once the processor has chosen and customized theprofile, the processor 360 is ready to modulate the power from the powersupply 366 to the penetrating member driver 368 through an amplifier370. The processor 360 may measure the location of the penetratingmember 372 using a position sensing mechanism 374 through an analog todigital converter 376 linear encoder or other such transducer. Examplesof position sensing mechanisms have been described in the embodimentsabove and may be found in the specification for commonly assigned,copending U.S. patent application Ser. No. 10/127,395, filed Apr. 19,2002 and previously incorporated herein. The processor 360 calculatesthe movement of the penetrating member by comparing the actual profileof the penetrating member to the predetermined profile. The processor360 modulates the power to the penetrating member driver 368 through asignal generator 378, which may control the amplifier 370 so that theactual velocity profile of the penetrating member does not exceed thepredetermined profile by more than a preset error limit. The error limitis the accuracy in the control of the penetrating member.

After the lancing event, the processor 360 can allow the user to rankthe results of the lancing event. The processor 360 stores these resultsand constructs a database 80 for the individual user. Using the database379, the processor 360 calculates the profile traits such as degree ofpainlessness, success rate, and blood volume for various profiles 362depending on user input information 364 to optimize the profile to theindividual user for subsequent lancing cycles. These profile traitsdepend on the characteristic phases of penetrating member advancementand retraction. The processor 360 uses these calculations to optimizeprofiles 362 for each user. In addition to user input information 364,an internal clock allows storage in the database 379 of information suchas the time of day to generate a time stamp for the lancing event andthe time between lancing events to anticipate the user's diurnal needs.The database stores information and statistics for each user and eachprofile that particular user uses.

In addition to varying the profiles, the processor 360 can be used tocalculate the appropriate penetrating member diameter and geometrysuitable to realize the blood volume required by the user. For example,if the user requires about 1-5 microliter volume of blood, the processor360 may select a 200 micron diameter penetrating member to achieve theseresults. For each class of penetrating member, both diameter andpenetrating member tip geometry, is stored in the processor 360 tocorrespond with upper and lower limits of attainable blood volume basedon the predetermined displacement and velocity profiles.

The lancing device is capable of prompting the user for information atthe beginning and the end of the lancing event to more adequately suitthe user. The goal is to either change to a different profile or modifyan existing profile. Once the profile is set, the force driving thepenetrating member is varied during advancement and retraction to followthe profile. The method of lancing using the lancing device comprisesselecting a profile, lancing according to the selected profile,determining lancing profile traits for each characteristic phase of thelancing cycle, and optimizing profile traits for subsequent lancingevents.

An article titled Artificial Muscles in the October 2003 issue ofScientific American is incorporated herein by reference for allpurposes.

Referring now to FIG. 27, yet another embodiment of the presentinvention will now be discussed. Mathematical modeling of microscaleprocesses is a uniquely useful alternative to the known approaches sincethe chemical and physical processes in the microscale generally followdeterministic physical laws that can be accurately represented inmathematical models. Once validated by external measurements, modelingcan predict internal behavior at any point in space and time within themicrodevice, leading to new insights and optimization techniques, e.g.,the accurate fitting of non-linear response functions, optimization ofsystem dynamics, or location of a specific region of incomplete reagentmixing, complete with design modifications that will remedy the problem.

Many developers of microdevices utilize this very powerful approach ofsimultaneous modeling and experimentation. Microscale fluid movers havebeen developed using both linear³⁻⁵ and nonlinear⁶⁻⁸ modeling, even whencomplex fluids such as particle suspensions^(10,11) are involved. Othercomponents of microfluidic systems¹²⁻¹⁷ have benefited from this dualapproach as well.

The large surface-to-volume ratio characteristic of microdevices,however, frequently leads to unexpected behaviors. For example,microvolumes of physiological fluids evaporate, cool, and heat extremelyrapidly and modeling is often desirable to accommodate, or leverage,such heat transfer and evaporation processes and their impact on thesystem. At the typical low Reynolds-number (slow flows) in microdevices,mixing is often problematic and modeling guides the design to achievemixing requirements.

The modeling of laminar flow is rarely an end in itself, but since theexact governing equations can be solved analytically in simple channels,or numerically in more complex channels, this produces valuableknowledge of the flowfield and its effect on other important physicalprocesses, for example the precise control of chemical reaction rate bydesigning the diffusive mixing of the reactants. A multiphysics model isthe result and is extremely useful to experimentalists tasked withsorting out the effects of a microdevice with complex physics. Manyresearchers have utilized this approach to develop devices for fluidconstituent extraction¹⁸, property measurement such as pH¹⁹,viscosity²⁰, and diffusion coefficient²¹, quantitative analysis²²,sample preparation²³, and laminate-based microfluidic devices forbiomedical applications²⁴⁻²⁸.

To illustrate how modeling can speed the development of diagnosticproducts, the present application discusses using one embodiment of thepresent invention to model a microscale processes to speed developmentof a microfabricated glucose detecting member.

Referring now to FIGS. 27A and 27B, effort has been made to develop anovel microfabricated point-of-use glucose detecting member to beintegrated within an automated low-volume lancet-based blood collectiondevice. In a nonlimiting embodiment, the blood collection device isoptimized to achieve almost painless blood acquisition of approximately200 mL per sample ( 1/100^(th) of a drop of blood). It should beunderstood, of course, that other volumes such as about 500 nl, 400 nl,300 nl, 200 nl, 100 nl, 60 nl or less can also be used in otherembodiments of the invention. A new integrated glucose detecting memberwas developed to be compatible with such small fluid volumes, as wellas, for example and not limitation, a sub-10 second response time and anaccuracy of ±5% over the clinical range. FIG. 27B shows one embodimentof the prototype analyte detecting member arrangement as well as theintegrated glucose lancing device. The analyte detecting members may beclustered in units of five for each sample measurement and within amicrochannel along which a blood sample flows.

The present invention focuses here on the analyte detecting memberitself, a new type of fluorescence-optical glucose biosensor. In oneembodiment, the membrane comprises an emulsion that incorporates theenzyme glucose oxidase (GOX) to catalytically consume sample glucose andco-consume oxygen. The emulsion additionally contains anoxygen-quenchable fluorescent indicator that determines theconcentration, and hence consumption, of oxygen within the analytedetecting member by a change in fluorescence and thus is related to thesample glucose concentration. The indicator is contained in dispersedhydrophobic droplets within a hydrophilic matrix containing GOX. The useof an emulsion enables single-step deposition of the analyte detectingmember, avoiding much complexity in manufacturing and maintains optimalmicro-environments for the GOX and the fluorescent indicator. Othersignificant advantages such as faster response times are expected.

The analyte detecting member model mathematically replicates thesignificant physical and chemical processes taking place in the analytedetecting member and sample. FIG. 28 provides a simplified schematic ofthe most important processes.

Prior to contact between the sample and the analyte detecting memberlayers, the whole blood sample contains red blood cells (RBCs) at agiven hematocrit level and plasma with dissolved oxygen (bound tohemoglobin inside the RBCs and equilibrated with the surroundingplasma), human catalase (with no significant exchange of catalasebetween RBCs and plasma), glucose (which is the analyte), and hydrogenperoxide. In this embodiment, the sample is assumed to contain no GOX atthis point. Other blood constituents that diffuse into the analytedetecting member layer are not expected to have a significant impact onthe analyte detecting member chemistry at the concentrations they canreach within 60 seconds after exposure.

Prior to sample contact, the analyte detecting member membrane(dispersed-phase) contains a fluorescent indicator in the form of aruthenium complex immobilized within microdroplets of a hydrophobicmaterial (a siloxane-containing polymer) that are of known concentrationand size distribution and embedded in a continuous hydrogel matrix ofknown water, polymer, and GOX content (see photo in FIG. 28). Themembrane additionally has an oxygen concentration in equilibrium withthe atmosphere.

When the analyte detecting member is initially exposed to the sample,the diffusion of all species is affected by the presence of thedispersed hydrophobic droplets; depending on the diffusion and partitioncoefficient of the each diffusing species, their diffusion rate may beincreased or decreased. GOX starts to diffuse out of the analytedetecting member and into the sample at a slower rate than that of thesmall diffusants. As the glucose molecules reach the GOX molecules, theyare metabolized and converted, with the co-consumption of oxygen andproduction of hydrogen peroxide, to gluconic acid, which in turn isinstantaneously and non-reversibly hydrolyzed to gluconolactone.

In the present embodiment, the ruthenium complex(ruthenium-diphenylphenantroline Ru(dpp)₃ ²⁺) in the hydrophobicmicrodroplets is initially in equilibrium with the ambient oxygenconcentration, and its fluorescent lifetime is quenched to some degree.As oxygen is consumed by the GOX enzyme reaction a concentrationgradient is generated between the hydrophobic microdroplets and thesurrounding hydrogel, causing the diffusion of oxygen out of themicrodroplets. At the same time, oxygen from the plasma in the sample(continually replenished by the RBCS) is diffusing into the analytedetecting member and locally counteracting the reduction in oxygenconcentration accomplished by the GOX enzyme reaction. The net effect isa location-dependent reduction in the oxygen concentration in themicrodroplets. The dispersed ruthenium complex within the microdropletsis thus quenched to a value somewhere between the values for ambient andfor about 0 mbar oxygen. By way of example and not limitation,fluorescence lifetimes for these systems tend to be in the lowmicrosecond range.

Modeling Methodology

In one embodiment of the present invention, the analyte detecting membermodel mathematically implements the physics of the analyte detectingmember as described above. It divides the assay time into small timesteps and the analyte detecting member into small control volumes. Byway of example and not limitation, in the current embodiment, duringeach time step (and in each control volume), the model simultaneouslysolves a specie conservation equation for each important constituent:oxygen, glucose, glucose oxidase, catalase, and hydrogen peroxide. Eachconservation equation includes an accumulation term, a diffusion term,and a production/destruction term. The latter relies on a productionrate calculated either as a Michaelis-Menton reaction (catalase) orPing-Pong Bi-Bi reaction (glucose oxidase).

The analyte detecting member model may track the diffusion of eachimportant chemical component of the emulsion and sample, the chemicalreactions between them, and the resulting signal from oxygen depletion.When the oxygen mass transfer rate between the hydrophobic droplet andsurrounding hydrogel is as fast as the mass transfer rate of oxygen andglucose in the hydrophilic phase by diffusion, the concentration ofoxygen in a droplet and the surrounding hydrophilic phase will always beclose to equilibrium. This depends mainly on droplet diameter anddiffusion coefficients, and is true for this analyte detecting memberemulsion when the droplets are less than 5 microns in diameter. Thisrapid equilibration allows a welcome simplification in that the emulsioncan be considered a single continuous material with averaged properties,instead of two segregated materials, one for each phase, requiringconstant updating of the local oxygen flux between them.

Thus, the analyte detecting member model treats the emulsion as acontinuum with properties based on volume-fraction averages of theproperties of the hydrophobic and hydrophilic phases. Thevolume-averaged properties include: diffusion coefficient, solubility,and initial concentrations of each conserved chemical species. Usingoxygen concentration in the analyte detecting member membrane as anexample, the initial concentration (mM) is[O₂ ]=f _(Aq)S_(O2 Aq) +f _(Si)S_(O2 Si),

the effective partition coefficient is

${H_{O\; 2} = {f_{Aq} + {f_{Si}\frac{S_{O\; 2{Si}}}{S_{O\; 2\;{Aq}}}}}},$

and the diffusion coefficientD_(O2) =f _(Ag)D_(O2 Aq) +f _(Poly)(1−f _(Si))D_(O2 Poly) +f_(Si)D_(O2 Si)

where f_(Si) is the volume fraction of the emulsion that is hydrophobicphase, f_(Aq) and f_(Poly) are the volume fractions of the hydrophilicphase that are aqueous and polymer, respectively. The diffusioncoefficients of oxygen in water, hydrogel polymer, and hydrophobic phaseare D_(O2 Aq), D_(O2 Poly), and D_(O2 Si). Finally, the solubilities ofoxygen in water and hydrophobic phase at initial conditions areS_(O2 Aq) and S_(O2 Si) in mM units.

Solution of each constituent's conservation equation, each impacted bychemical reactions with other constituents, produces the predictedconcentrations of oxygen, glucose, glucose oxidase, catalase, andhydrogen peroxide at every location in the analyte detecting membermembrane and sample, as shown in the FIGS. 29 to 33.

Results from Model and Experiment

The following sets of plots illustrate some of the information generatedby the model and the corresponding experiment for one set of initialconditions and analyte detecting member parameters. In these plots weused glucose-loaded saline solutions to provide tightly-controlledsamples.

FIG. 29 a shows the reaction rate for catalase from Aspergillus niger(as contaminant of GOX) and, in FIG. 29 b, glucose oxidase fromAspergillus niger as a function of cross-sectional distance through thesample (1 mm on the left) and analyte detecting member (0.047 mm).Enzyme reaction rates are in mM/s. The curves correspond to 5, 10, 15,and 20 seconds after the exposure of the analyte detecting membermembrane to the sample. Both reactions occur almost solely in theanalyte detecting member; their initial rates are the highest.

FIG. 30 shows the concentration of glucose oxidase from Aspergillusniger (FIG. 30 a), and concentration of catalase from Aspergillus niger(as contaminant of GOX) (FIG. 30 b) across a sample and analytedetecting member cross section. Experiments have shown that the A. nigerenzymes are somewhat immobilized in the analyte detecting memberemulsion by an as yet unknown mechanism (possibly entrapment), diffusingapproximately 10³ times more slowly than if free. This reduction isimplemented in the model, which only allows the normal diffusion speedin the sample. For the figures, Concentrations profile of enzymes are inmM.

FIGS. 31 a-31 c show the concentrations of the reactants: oxygen, freelydissolved in sample and analyte detecting member emulsion (FIG. 31 a),and hydrogen peroxide (FIG. 31 b) and glucose (FIG. 31 c), both freelydissolved in sample and analyte detecting member hydrophilic phase. Forthe figures, concentrations of reactants are in mM. These concentrationsare affected by both diffusion and the consumption/production bychemical reactions over time. The decrease in oxygen concentration inthe hydrophobic phase is the cause of the change in fluorescencelifetime. FIG. 31 b shows an increase in hydrogen peroxide concentrationproduced by the glucose oxidase activity; hydrogen peroxide thatdiffuses into the sample largely escapes the catalase reaction.

FIG. 32 shows the change in fluorescence lifetime as a function ofanalyte detecting member response to glucose.

FIGS. 33 a and 33 b shows the simulated dynamic response of an analytedetecting member with good overall response characteristics: fastresponse, dynamic range in the physiologically important range, and alarge enough signal change to be useful. The analyte detecting memberhas a hydrophobic to hydrophilic volume fraction of 40/60, an overallthickness of 47 micrometers, and 70% water in the hydrophilic phase.

FIG. 33 a shows a simulated calibration graph, plotted for differenttimes after initial analyte detecting member exposure. The analytedetecting member shows a solid response over the whole glucose range inless than 10 seconds. FIG. 33 b shows simulated response curves, plottedfor different glucose concentrations. In the present embodiment, theanalyte detecting member reaches a plateau for the high glucose levelafter less than 10 seconds, while the medium and low glucose levels showan acceptable response over a similar time (in kinetic measurementmode). For reference, the normal range of glucose concentration incapillary blood is 3.5-6 mM. The 25 mM case represents an extremelyhigh, critical glucose level. In FIG. 33 b, the signal for even the highglucose level never reaches a signal of 100%, which would be equivalentto complete consumption of all oxygen present in the analyte detectingmember, but rather a steady state value above 95%. The discrepancy isdue to oxygen diffusion from the sample. The fact that oxygen diffusionis relatively minor is advantageous as the analyte detecting member willnot be significantly sensitive to variations in oxygen concentrations inthe sample.

FIG. 34 shows test data taken with a prototype analyte detecting membermembrane using the same initial conditions and analyte detecting memberparameters as supplied to the analyte detecting member model for thepreceding figures. The predicted response (FIG. 33 b) agrees with thetest data, especially at the higher glucose loading. The data from theprototype membrane displays some variability and a slightly reduceddynamic range compared to that predicted.

The model was highly useful in the beginning of the development projectto predict that rapid (sub-10 second) response was indeed possible (at atime when the experiments still showed response time of minutes due tomaterial incompatibilities that were later corrected).

For the present embodiment, it was also discovered through modeling thatGOX activity at concentrations higher than 3-5 mM in the analytedetecting member layer were highly non-linear, and that there was aninhibitory effect on GOX activity at those concentrations. This freedthe experimental teams from trying to push the GOX concentration in theanalyte detecting member to the solubility limit.

For manufacturing purposes, in some embodiments, the analyte detectingmembers were designed so that were less than 50 micrometers thin. Themodel, however, had predicted an optimum balance between response timeand cross-sensitivity to sample oxygen for a analyte detecting member ofapproximately 100 micrometers thickness. It should be understood, ofcourse, that various thicknesses may be used with different deviceswithout deviating from the scope of the invention. So the model wasexercised repeatedly to explore the design space; it predicted that ifthe GOX concentration was changed to 3 mM it would be possible toachieve a similar balance between fast response time, good dynamicrange, and low cross sensitivity.

A particularly puzzling phenomenon was discovered when the experimentalteams noticed a significant drop-off of glucose signal (an increase influorescence lifetime, or more accurately, in hybrid fluorescencephosphorescence lifetime) after only short exposure of the analytedetecting member to the sample. It was discovered through modeling thatthe analyte detecting member had in fact “used up” all the glucose inthe sample solution, and the volume of the sample was subsequentlyincreased.

The discussion of the various optima for the analyte detecting memberand their derivation from the model are beyond the scope of this paperand will be reported elsewhere. However, based on multiple model runsand their experimental verification, we have assembled a number ofqualitative design rules that should be generally applicable.

The thickness of the whole blood sample layer has no significant effectunless sample layer is very thin (<100 micrometers) and is not shieldedfrom the atmosphere.

In one embodiment, a thinner analyte detecting member will be faster,but oxygen diffusion from the sample will start to be noticeable foranalyte detecting members thinner than 100 micrometers. A higher GOXconcentration can compensate for this effect. Oxygen orglucose-controlled GOX behavior is not a function of layer thickness butof the ratio between hydrophilic and hydrophobic volume and GOXconcentration.

GOX concentration has to be balanced with the hydrophobic phase volumefraction to ensure a good dynamic range as well as a glucose-controlledreaction mechanism.

A ratio of hydrophilic to hydrophobic phase of 80/20 is ideal, but thiscan be modified as long as GOX concentration is modified as well.Increasing the ratio has three effects that beneficially enhance eachother and decrease analyte detecting member response time: (a) fasterdiffusion of glucose in the hydrophilic phase (there is lessimpenetrable hydrophobic material in the way), (b) faster removal ofoxygen from the hydrophobic phase (because there is less stored oxygenavailable), and (c) a higher amount of GOX can be used, because there ismore hydrophilic phase.

Both layer thickness as well as the ratio of hydrophilic to hydrophobicphase will impact the overall fluorescence intensity that can beobtained form the analyte detecting member.

A low hydrogel polymer fraction (a higher water content) in the hydrogelyields analyte detecting members with faster response.

Catalase contamination in the hydrogel layer converts hydrogen peroxideback into oxygen, thus removing half of the oxygen-consuming effect thatthe consumption of glucose had on the hydrophobic layer. GOX with lowcatalase contamination is required.

Droplet sizes below 5 micrometers ensure oxygen diffusion inside thedroplets is not a controlling parameter.

While the invention has been described and illustrated with reference tocertain particular embodiments thereof, those skilled in the art willappreciate that various adaptations, changes, modifications,substitutions, deletions, or additions of procedures and protocols maybe made without departing from the spirit and scope of the invention.For example, with any of the above embodiments, the location of thepenetrating member drive device may be varied, relative to thepenetrating members or the cartridge. With any of the above embodiments,the penetrating member tips may be uncovered during actuation (i.e.penetrating members do not pierce the penetrating member enclosure orprotective foil during launch). With any of the above embodiments, thepenetrating members may be a bare penetrating member during launch. Withany of the above embodiments, the penetrating members may be barepenetrating members prior to launch as this may allow for significantlytighter densities of penetrating members. In some embodiments, thepenetrating members may be bent, curved, textured, shaped, or otherwisetreated at a proximal end or area to facilitate handling by an actuator.The penetrating member may be configured to have a notch or groove tofacilitate coupling to a gripper. The notch or groove may be formedalong an elongate portion of the penetrating member. With any of theabove embodiments, the cavity may be on the bottom or the top of thecartridge, with the gripper on the other side. In some embodiments,analyte detecting members may be printed on the top, bottom, or side ofthe cavities. The front end of the cartridge maybe in contact with auser during lancing. The same driver may be used for advancing andretraction of the penetrating member. The penetrating member may have adiameters and length suitable for obtaining the blood volumes describedherein. The penetrating member driver may also be in substantially thesame plane as the cartridge. The driver may use a through hole or otheropening to engage a proximal end of a penetrating member to actuate thepenetrating member along a path into and out of the tissue. The sensorymaterial may be deposited into the via holes. The conductor material mayalso be deposited into the via holes. The via holes may be formed by avariety of methods including micro drilling, laser drilling, plasmaetching, or the like.

Any of the features described in this application or any referencedisclosed herein may be adapted for use with any embodiment of thepresent invention. For example, the devices of the present invention mayalso be combined for use with injection penetrating members or needlesas described in commonly assigned, copending U.S. patent applicationSer. No. 10/127,395 filed Apr. 19, 2002. An analyte detecting member todetect the presence of foil may also be included in the lancingapparatus. For example, if a cavity has been used before, the foil orsterility barrier will be punched. The analyte detecting member candetect if the cavity is fresh or not based on the status of the barrier.It should be understood that in, optional embodiments, the sterilitybarrier may be designed to pierce a sterility barrier of thickness thatdoes not dull a tip of the penetrating member. The lancing apparatus mayalso use improved drive mechanisms. For example, a solenoid forcegenerator may be improved to try to increase the amount of force thesolenoid can generate for a given current. A solenoid for use with thepresent invention may have five coils and in the present embodiment theslug is roughly the size of two coils. One change is to increase thethickness of the outer metal shell or windings surround the coils. Byincreasing the thickness, the flux will also be increased. The slug maybe split; two smaller slugs may also be used and offset by ½ of a coilpitch. This allows more slugs to be approaching a coil where it could beaccelerated. This creates more events where a slug is approaching acoil, creating a more efficient system.

In another optional alternative embodiment, a gripper in the inner endof the protective cavity may hold the penetrating member during shipmentand after use, eliminating the feature of using the foil, protectiveend, or other part to retain the used penetrating member. Some otheradvantages of the disclosed embodiments and features of additionalembodiments include: same mechanism for transferring the usedpenetrating members to a storage area; a high number of penetratingmembers such as 25, 50, 75, 100, 500, or more penetrating members may beput on a disk or cartridge; molded body about a lancet becomesunnecessary; manufacturing of multiple penetrating member devices issimplified through the use of cartridges; handling is possible of barerods metal wires, without any additional structural features, to actuatethem into tissue; maintaining extreme (better than 50 micron-lateral-and better than 20 micron vertical) precision in guiding; and storagesystem for new and used penetrating members, with individualcavities/slots is provided. The housing of the lancing device may alsobe sized to be ergonomically pleasing. In one embodiment, the device hasa width of about 56 mm, a length of about 105 mm and a thickness ofabout 15 mm. Additionally, some embodiments of the present invention maybe used with non-electrical force generators or drive mechanism. Forexample, the punch device and methods for releasing the penetratingmembers from sterile enclosures could be adapted for use with springbased launchers. The gripper using a frictional coupling may also beadapted for use with other drive technologies.

Still further optional features may be included with the presentinvention. For example, with any of the above embodiments, the locationof the penetrating member drive device may be varied, relative to thepenetrating members or the cartridge. With any of the above embodiments,the penetrating member tips may be uncovered during actuation (i.e.penetrating members do not pierce the penetrating member enclosure orprotective foil during launch). The penetrating members may be a barepenetrating member during launch. In some embodiments, the penetratingmember may be a patent needle. The same driver may be used for advancingand retraction of the penetrating member. Different analyte detectingmembers detecting different ranges of glucose concentration, differentanalytes, or the like may be combined for use with each penetratingmember. Non-potentiometric measurement techniques may also be used foranalyte detection. For example, direct electron transfer of glucoseoxidase molecules adsorbed onto carbon nanotube powder microelectrodemay be used to measure glucose levels. In some embodiments, the analytedetecting members may formed to flush with the cartridge so that a“well” is not formed. In some other embodiments, the analyte detectingmembers may formed to be substantially flush (within 200 microns or 100microns) with the cartridge surfaces. In all methods, nanoscopic wiregrowth can be carried out via chemical vapor deposition (CVD). In all ofthe embodiments of the invention, preferred nanoscopic wires may benanotubes. Any method useful for depositing a glucose oxidase or otheranalyte detection material on a nanowire or nanotube may be used withthe present invention. Additionally, for some embodiments, any of thecartridge shown above may be configured without any of the penetratingmembers, so that the cartridge is simply an analyte detecting device.Still further, the indexing of the cartridge may be such that adjacentcavities may not necessarily be used serially or sequentially. As anonlimiting example, every second cavity may be used sequentially, whichmeans that the cartridge will go through two rotations before every orsubstantially all of the cavities are used. As another nonlimitingexample, a cavity that is 3 cavities away, 4 cavities away, or Ncavities away may be the next one used. This may allow for greaterseparation between cavities containing penetrating members that werejust used and a fresh penetrating member to be used next. It should beunderstood that the spring-based drivers shown in the present inventionmay be adapted for use with any of the cartridges shown herein such as,but not limited to, those shown in FIGS. 61 and 62. These spring-baseddrivers may also be paired with gripper blocks that are configured topenetrate into cartridges that fully seal penetrating member therein, inorder engage those penetrating members. The start and end positions ofthe penetrating members may also be the same. The penetrating membersmay be parked in a holder before actuation, and in some embodiments,into a holder after actuation (as seen in cartridge 500 or any othercartridge herein). Embodiments of the present invention may also includeguides which provide lateral constraints and/or vertical constraintsabout penetrating member. These constraints may be positioned about theshaft portions of the penetrating member. For any of the embodimentsherein, they may be configured to provide the various velocity profilesdescribed. The analyte detecting members may use volumes of less than 1microliter, less than 500 nl, 400 nl, 300 nl, 200 nl, 100 nl, 75 nl, 60nl, 50 nl, 40 nl, 30 nl, 20 nl, 10 nl, or less of body fluid. In someembodiments, the chamber that holds the body fluid over the electrodesis less than 1 microliter, less than 500 nl, 400 nl, 300 nl, 200 nl, 100nl, 75 nl, 60 nl, 50 nl, 40 nl, 30 nl, 20 nl, 10 nl, or less in volume.In still other embodiments, the volume of the chamber over theelectrodes is less than 1 microliter, less than 500 nl, 400 nl, 300 nl,200 nl, 100 nl, 75 nl, 60 nl, 50 nl, 40 nl, 30 nl, 20 nl, 10 nl, orless. Any of the features set forth in the present description may becombined with any other feature of the embodiments set forth above.

The publications discussed or cited herein are provided solely for theirdisclosure prior to the filing date of the present application. Thefollowing applications are incorporated herein by reference for allpurposes: Ser. Nos. 60/507,317, 60/507,852, 60/507,845, 60/507,690, and60/507,688. Nothing herein is to be construed as an admission that thepresent invention is not entitled to antedate such publication by virtueof prior invention. Further, the dates of publication provided may bedifferent from the actual publication dates which may need to beindependently confirmed. All publications and applications mentionedherein are incorporated herein by reference to disclose and describe thestructures and/or methods in connection with which the publications arecited.

Expected variations or differences in the results are contemplated inaccordance with the objects and practices of the present invention. Itis intended, therefore, that the invention be defined by the scope ofthe claims which follow and that such claims be interpreted as broadlyas is reasonable.

1. A body fluid sampling device comprising: a single cartridge; aplurality of penetrating members coupled to said single cartridge andoperatively couplable to the penetrating member driver, said penetratingmembers movable to extend radially outward from the cartridge topenetrate tissue; a plurality of analyte detecting members coupled tosaid single cartridge, wherein at least one of said analyte detectingmembers positioned on the cartridge to receive body fluid from a woundin the tissue created by a penetrating member when the cartridge is inan operative position; and a mesh structure pushed and pierced by thepenetrating member against the tissue in order to draw fluid generatedby said tissue towards one of the analyte detecting members and whereinthe mesh is a gradient mesh.
 2. The device of claim 1 further comprisinga ring around the cartridge wherein said analyte detecting members aremounted on said ring, along with said mesh.
 3. The device of claim 1further comprising a ring around the cartridge wherein said analytedetecting members are coupled to said cartridge through said ring. 4.The device of claim 1 further comprising a plurality of electrodescoupled to said analyte detecting member.
 5. The device of claim 1further comprising a radial cartridge, said support structure coupled tosaid radial cartridge.
 6. The device of claim 1 further comprising aplurality of electrodes each having said sensory material.
 7. The deviceof claim 1 wherein the texture structure is one or more of dimples,raised portions, detents, depressions, cross-hatch, scoring,criss-cross, and triangles.
 8. The device of claim 1 wherein the texturestructure improves user feedback and sensation of contact to let theuser know whether he/she is on target.
 9. The device of claim 1 whereinthe mesh structure is made of capillary fibers.
 10. The device of claim1 wherein the mesh structure is pliable enough to allow relaxation. 11.The device of claim 1 wherein the mesh structure distributes impact ofthe penetrating member on the tissue to increase cutting efficiency ofthe penetrating member.
 12. The device of claim 1 wherein the meshstructure reduces the amount of micropositioning used to assure that thedroplet of the fluid gets to the analyte detecting member by reducingthe amount of body fluid that spontaneously rises to the surface of theskin.
 13. The device of claim 1 wherein the mesh structure is ahydrophilic mesh that allows the fluid built up on tissue to beabsorbed.
 14. A body fluid sampling device comprising: a singlecartridge; a plurality of penetrating members coupled to said singlecartridge and operatively couplable to the penetrating member driver,said penetrating members movable to extend radially outward from thecartridge to penetrate tissue; a plurality of analyte detecting memberscoupled to said single cartridge, wherein at least one of said analytedetecting members positioned on the cartridge to receive body fluid froma wound in the tissue created by a penetrating member when the cartridgeis in an operative position; and a mesh structure pushed and pierced bythe penetrating member against the tissue in order to draw fluidgenerated by said tissue towards one of the analyte detecting members;and wherein the mesh structure is a gradient type of mesh designed andpatterned to create a desired movement of fluid in contact with themesh.